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<html lang="en">
<head>
    <meta charset="UTF-8">
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    <title>Document</title>
</head>
<body>

    <div id="app"></div>

    <script src="react.js"></script>
    <script src="react-dom.js"></script>
    <script src="browser.min.js"></script>
    <script type="text/babel">
    
    function MailBox(props) {
        const unreadMessages = props.unreadMessages;
        return (
            <div>
            <h1>Hello!</h1>
            {unreadMessages.length>0 &&
            <h2>You have {unreadMessages.length}unread message</h2>
            }
            </div>
        )
        
    }
    const message = ["React","Re:React","Re:Re:React"];
    ReactDOM.render(
        <MailBox unreadMessages = {message} />,
        document.getElementById("app")
    )
    
    </script>
    
</body>
</html>